Cryptography involves techniques for secure communication between two or more nodes. A node may include a mobile communication device, a tablet computer, a laptop computer, desktop, other forms of computing devices and communication devices, a server device in a network, a client device in a network, one or more nodes in a distributed network, etc. The nodes may be associated with a natural person, a group of people such as employees of a company, a system such as a banking system, etc.
In some cases, the two or more nodes may be linked by a communications network that is unsecure. For example, the two nodes may be linked by a communications network where a third party may be able to eavesdrop on the communication between the nodes. Therefore, messages sent between nodes can be sent in encrypted form and where, upon receipt, the intended recipients may decrypt the messages with corresponding decryption key(s) (or other decryption methods). Thus the security of such communication may be dependent on preventing the third party from determining the corresponding decryption key.
One method of cryptography includes using symmetric-key algorithms. The keys are symmetric in the sense that the same symmetric-key is used for both encryption of a plain text message and decryption of cipher text. One consideration of using symmetric-key algorithms is how to transmit the symmetric-key to both nodes in a secure way to prevent an eavesdropper from acquiring the symmetric-key. This may include, for example, physically delivering the symmetric-key to the (authorised) nodes so that the symmetric-key is never transmitted over an unsecure communications network. However, physical delivery in not always an option. Therefore a problem in such cryptographic systems is the establishment of the symmetric-key (which may be based on a common secret) between the nodes across an unsecure network. In recent times, situations may make it desirable that transmission of keys is usually done electronically over communications systems such as the internet. Thus this step of providing a shared secret (e.g. the symmetric-key) is a potentially catastrophic vulnerability. As the symmetric-key algorithms (and protocols) are simple and widely used, there is a need for an ability for two nodes to determine a common secret key securely across an unsecure network.
Other existing cryptography methods include using asymmetric-keys. These may be used in public-key cryptography where they asymmetric-keys include a private key and a corresponding public key. The public key may be made publicly available whereas the private key, as the name implies, is kept private. These asymmetric-keys may be used for public-key encryption and for digital signature amongst other things. Existing protocols include as the Diffie-Hellman Key Exchange and the Three Pass Protocol enable the secure sharing of a secret across unsecure networks. However these methods are computationally expensive in some cases, such as where new secrets are to be continuously generated and shared.
Alternative asymmetric key hierarchies (such as described in the Bitcoin Developer's Guide) rely on a random seed and an index structure resulting in poor key management. In contrast, embodiments of the present invention may comprise the use of meaningful ‘messages’ (M) to not only generate asymmetric keys but also deterministic hierarchical shared secrets which are provably associated with specific data.
Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.